CH346535A - Process for purifying dimethyl terephthalate - Google Patents
Process for purifying dimethyl terephthalateInfo
- Publication number
- CH346535A CH346535A CH346535DA CH346535A CH 346535 A CH346535 A CH 346535A CH 346535D A CH346535D A CH 346535DA CH 346535 A CH346535 A CH 346535A
- Authority
- CH
- Switzerland
- Prior art keywords
- dimethyl terephthalate
- distillation
- purifying dimethyl
- terephthalate
- glycol
- Prior art date
Links
- WOZVHXUHUFLZGK-UHFFFAOYSA-N dimethyl terephthalate Chemical compound COC(=O)C1=CC=C(C(=O)OC)C=C1 WOZVHXUHUFLZGK-UHFFFAOYSA-N 0.000 title claims description 26
- 238000000034 method Methods 0.000 title claims description 5
- 238000004821 distillation Methods 0.000 claims description 10
- -1 alkylene glycols Chemical class 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 4
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 14
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 4
- 238000000746 purification Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 2
- 238000006068 polycondensation reaction Methods 0.000 description 2
- 229920000139 polyethylene terephthalate Polymers 0.000 description 2
- 239000005020 polyethylene terephthalate Substances 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- 238000005809 transesterification reaction Methods 0.000 description 2
- 230000001133 acceleration Effects 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000032050 esterification Effects 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- OJURWUUOVGOHJZ-UHFFFAOYSA-N methyl 2-[(2-acetyloxyphenyl)methyl-[2-[(2-acetyloxyphenyl)methyl-(2-methoxy-2-oxoethyl)amino]ethyl]amino]acetate Chemical compound C=1C=CC=C(OC(C)=O)C=1CN(CC(=O)OC)CCN(CC(=O)OC)CC1=CC=CC=C1OC(C)=O OJURWUUOVGOHJZ-UHFFFAOYSA-N 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
- 238000010626 work up procedure Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/62—Use of additives, e.g. for stabilisation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
- C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Description
Verfahren zum Reinigen von Dimethylterephthalat Die Reinigung von Dimethylterephthalat kann entweder durch Destillation oder durch Umkristalli sation, z. B. aus Methanol oder Tetrachlorkohlen- stoff, vorgenommen werden. Bei der Destillation unter Atmosphärendruck wird eine extreme Reinigung des wegen nicht erreicht, weil bei den relativ hohen Temperaturen Zersetzungserscheinungen unvermeid bar sind, welche neuerliche Verunreinigungen hervor rufen. Der Nachteil bei der Umkristallisation liegt darin, dass grosse Mengen Mutterlauge anfallen, deren Aufarbeitung umständlich ist und erhebliche Verluste nach sich zieht.
Man hat bereits vorgeschlagen, die Destillation von Dimethylterephthalat in einem konti nuierlichen Prozess durchzuführen, wobei drei Destilla- tionszonen durchlaufen werden. Auch diese Art der Reinigung ist wegen der umfangreichen Apparaturen umständlich und lässt keine extreme Reinigung zu, wie sie für die Weiterverarbeitung von Dimethyl- terephthalat zu entsprechenden Polykondensaten un bedingt notwendig ist.
Es wurde gefunden, dass man das rohe Dimethyl- terephthalat einer weitgehenden Reinigung unter ziehen kann, wenn man es in'Gegenwart von Alkylen- glykolen, insbesondere Äthylenglykol, unter Vakuum einer Destillation unterwirft. Dieser Befund ist deshalb überraschend, weil durch eine Destillation z. B. mit Methanol keine Reinigung in gewünschtem Sinne möglich ist. Beim vorliegenden Verfahren wird er reicht, dass der rohe Dimethylester, welcher z.
B. durch Depolymerisation von Polyäthylenterephthalat oder durch Veresterung von Terephthalsäure gewonnen wurde, in einem Arbeitsgang destillativ gereinigt wird. Das zur Destillation verwendete Glykol kann sofort wieder zur weiteren Destillation verwendet werden, ohne dass es vorher redestilliert wird.
Der geringe Glykolgehalt des durch Abnutschen vom über schüssigen Glykol befreiten Dimethylterephthalats macht jede Zwischentrocknung überflüssig und be deutet eine wesentliche Beschleunigung des gesamten Arbeitsvorganges. Das Dimethylterephthalat ist sofort zur Ümesterung bzw. anschliessenden Polykonden sation zu Polyäthylenterephthalat geeignet. Man er hält Polykondensate hoher Viskositätsgrade mit K- Werten von 50 bis 57.
<I>Beispiel</I> 30 g rohes Dimethylterephthalat werden mit 270 g Äthylenglykol in einem Kolben gemischt und unter Einleiten von trockenem Stickstoff in einer Kolonne von 30 cm bei etwa 44 Torr destilliert. Das Azeotrop, welches aus etwa 97% Dimethylterephthalat besteht, geht bei etwa 120 in eine gekühlte Vorlage über. Das durch Absaugen von Glykol abgetrennte Dimethyl- terephthalat kann sofort zur Umesterung bzw. zur Polykondensation verwendet werden.
Process for purifying dimethyl terephthalate The purification of dimethyl terephthalate can be carried out either by distillation or by recrystallization, e.g. B. made of methanol or carbon tetrachloride. In the case of distillation under atmospheric pressure, extreme purification is not achieved because, at the relatively high temperatures, decomposition phenomena are inevitable, which cause renewed impurities. The disadvantage of recrystallization is that large amounts of mother liquor are produced, which are laborious to work up and result in considerable losses.
It has already been proposed to carry out the distillation of dimethyl terephthalate in a continuous process, with three distillation zones being passed through. This type of cleaning is also cumbersome because of the extensive equipment and does not permit extreme cleaning, as is absolutely necessary for the further processing of dimethyl terephthalate to corresponding polycondensates.
It has been found that the crude dimethyl terephthalate can be subjected to extensive purification if it is subjected to distillation in vacuo in the presence of alkylene glycols, in particular ethylene glycol. This finding is surprising because a distillation z. B. with methanol no cleaning in the desired sense is possible. In the present process, it is sufficient that the crude dimethyl ester, which z.
B. was obtained by depolymerization of polyethylene terephthalate or by esterification of terephthalic acid, is purified by distillation in one operation. The glycol used for the distillation can be used again immediately for further distillation without being redistilled beforehand.
The low glycol content of the dimethyl terephthalate freed from excess glycol by suction filtration makes any intermediate drying unnecessary and signifies a significant acceleration of the entire work process. The dimethyl terephthalate is immediately suitable for transesterification or subsequent polycondensation to polyethylene terephthalate. He holds polycondensates of high viscosity with K values of 50 to 57.
<I> Example </I> 30 g of crude dimethyl terephthalate are mixed with 270 g of ethylene glycol in a flask and distilled while introducing dry nitrogen in a column of 30 cm at about 44 torr. The azeotrope, which consists of about 97% dimethyl terephthalate, passes over into a cooled receiver at about 120. The dimethyl terephthalate separated by sucking off glycol can be used immediately for transesterification or for polycondensation.
Claims (1)
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEV9752A DE1004162B (en) | 1955-11-18 | 1955-11-18 | Process for purifying dimethyl terephthalate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CH346535A true CH346535A (en) | 1960-05-31 |
Family
ID=7572808
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CH346535D CH346535A (en) | 1955-11-18 | 1956-09-27 | Process for purifying dimethyl terephthalate |
Country Status (5)
| Country | Link |
|---|---|
| BE (1) | BE551364A (en) |
| CH (1) | CH346535A (en) |
| DE (1) | DE1004162B (en) |
| FR (1) | FR1163410A (en) |
| GB (1) | GB802067A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3468763A (en) * | 1966-06-21 | 1969-09-23 | Halcon International Inc | Purification of terephthalonitrile by azeotropic distillation with ethylene glycol |
-
1955
- 1955-11-18 DE DEV9752A patent/DE1004162B/en active Pending
-
1956
- 1956-09-27 CH CH346535D patent/CH346535A/en unknown
- 1956-09-28 BE BE551364A patent/BE551364A/en unknown
- 1956-10-08 FR FR1163410A patent/FR1163410A/en not_active Expired
- 1956-10-25 GB GB32597/56A patent/GB802067A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BE551364A (en) | 1959-12-18 |
| FR1163410A (en) | 1958-09-25 |
| GB802067A (en) | 1958-09-24 |
| DE1004162B (en) | 1957-03-14 |
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